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Full Discussion: Serial Lines Explained
Top Forums UNIX for Dummies Questions & Answers Serial Lines Explained Post 302930455 by sreyan32 on Sunday 4th of January 2015 11:15:36 AM
Old 01-04-2015
Okay from what I have read in this thread I can understand that in the older days you would have a monitor and a keyboard with a serial port connecting to the central CPU. You would communicate with the CPU using signals sent via the serial port. I know this is an over simplification but is it correct ?

Can someone explain how serial ports can be used for session control in a little more detail ?

What baffles me is that is why still use serial ports ? Why not remove them ? On a normal desktop or laptop serial ports are not used the way they were used back in the olden days, so keep them ?

For example as Corona688 mentioned in a earlier thread
stty still gives the baud rate. This is not required so why still keep it.

Why adopt an old standard forcefully when it is not required is my point
 

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CZ(4)							   BSD Kernel Interfaces Manual 						     CZ(4)

NAME
cz -- Cyclades-Z series multi-port serial adapter device driver SYNOPSIS
cz* at pci? dev ? function ? DESCRIPTION
The cz device driver supports the Cyclades-Z series of multi-port serial adapters. The Cyclades-Z is an intelligent serial controller com- prising: o PLX9060ES PCI bus interface o Xilinx XC5204 FPGA o IDT R3052 MIPS CPU The MIPS CPU runs firmware provided by the device driver. Communication with the MIPS is performed by modifying data structures located in board local RAM or host RAM. The Cyclades-Z comes in three basic flavors: o Cyclades-8Zo rev. 1 -- This is an older 8-port board with no FPGA. The serial ports are provided by an octopus cable. o Cyclades-8Zo rev. 2 -- This is the newer 8-port board. The serial ports are provided by an octopus cable. o Cyclades-Ze -- This is the expandable version of the Cyclades-Z. It uses an HD-50 SCSI cable to connect the board to a 1U rack mountable serial expansion box. Each box has 16 RJ45 serial ports, and up to 4 boxes may be chained together, for a total of 64 ports. Boxes 3 and 4 require their own external power supply, otherwise the firmware will refuse to start (as it cannot communi- cate with the UARTs in those boxes). The Cyclades-Z has several features to improve performance under high serial I/O load: o The board may operate in interrupt-driven mode or polled mode to reduce interrupt load. o Each channel has a large input and output buffer. o Each channel may be programmed to generate an interrupt based on reception of a specific character, e.g. a PPP End-Of-Frame charac- ter. o The MIPS CPU on the board performs all flow-control handling. FILES
/dev/ttyCZnnnn -- dial-in (normal) TTY device /dev/dtyCZnnnn -- dial-out TTY device SEE ALSO
pci(4), termios(4), tty(4) HISTORY
The cz driver first appeared in NetBSD 1.5. AUTHORS
The cz driver was written by Jason R. Thorpe <thorpej@zembu.com> and Bill Studenmund <wrstuden@zembu.com> of Zembu Labs, Inc. BUGS
The cz driver does not currently implement communication via host RAM. While this may improve performance by reducing the number of PCI mem- ory space read/write cycles, it is not straightforward to implement with the current bus_dma(9) API. Interrupt mode has not been tested. There is no support for reading or writing the EEPROM connected to the PLX PCI bus controller. BSD
May 17, 2000 BSD
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